1. Field of the Invention
The present invention relates to a communication control apparatus for transmitting analog and digital data.
2. Description of Background Art
As an example of a communication control apparatus, a control system employed in a vehicle for controlling a plurality of pieces of electrical equipment mounted on the vehicle is disclosed in Japanese Patent Laid-Open No. Hei6-276570. The disclosed vehicle control system comprises a plurality of input/output means and a central control means. The input/output means include: a sensor output reading means for fetching signals output by sensors installed on the electrical equipment; an input data generating means for generating input data from an output of the sensor output reading means; and 1st communication means each for converting an output of the input data generating means into a signal having a transmission format set in advance and outputting the signal to a data communication network as well as for extracting an energerization signal for energizing the electrical equipment from a signal received from the data communication network.
On the other hand, the central control means comprises a 2nd communication means connected to the data communication network and a control means for controlling the electrical equipment through the 2nd communication means. Connected to the data communication network, the 2nd communication means is used for exchanging data with each of the 1st communication means.
By virtue of the vehicle control system described above, the number of microcomputers in use can be reduced, allowing the manufacturing cost of the electrical equipment employed in the vehicle to be cut as well.
In addition, the number of I/O ports provided on the central control means and the number of lines connecting the I/O ports on the central control means to the input/output means can also be reduced, allowing the central control means to have a compact construction. Furthermore, a change in input/output means specification entailing a replacement can be implemented by adding or removing lines connecting the I/O ports to the input/output means. As a result, the development efficiency can also be improved as well.
The disclosure described above also reveals an embodiment wherein an analog signal output by a steering wheel angle sensor is converted into digital data by means of an A/D converter for carrying out analog to digital conversion and the digital data is then transmitted to the central control unit.
In the conventional communication control apparatus, if the number of sensors each for outputting an analog signal is increased, it is necessary to provide as many additional A/D converters as sensors newly added. It is thus desirable to provide a communication control apparatus which allows a common A/D converter of a common A/D conversion unit to be shared among a plurality of sensors.